In the handling and processing of dry, free flowing particulate materials such as powder, granules, chips, flakes, cubes and pellets, rotary valves commonly are used in metering and feeding such materials. They normally are used with bins, tanks, mixers, silos, classifiers, dryers, collectors, hoppers, cyclone separators, dust collectors and other equipment for pneumatic systems and process operations in various industries. Such valves typically consist of a housing having a cylindrical chamber provided with a material inlet opening and a material outlet opening, a shaft journaled in the housing and extending through the chamber and a rotor mounted on the shaft adapted to receive product fed through the material inlet opening and discharge such material through the outlet opening. The rotor generally consists of a pair of end walls or shrouds and a plurality of radially disposed, circumferentially spaced vanes cooperating with the end walls thereof to form a plurality of pockets which receive material through the inlet opening, convey the material through the rotor chamber and discharge it through the outlet opening. Such valves typically are installed between material holding vessels and pneumatic conveying systems for metering or otherwise feeding amounts of materials from a vessel into a material conveying line.
In the use of such valves, it has been found that a certain amount of the material being fed through the valve, and particularly materials having large particle sizes, become drawn by the rotors between ends of the rotor vanes and the cylindrical wall of the rotor chamber which results either in the shearing of the material particles or, in more severe cases, a jamming of the rotor thus interfering with the operation of the valves.
Many attempts have been made to redesign the feed arrangements of such valves to eliminate such shearing of the material being processed and/or prevent the jamming of such valves but such designs have not proven to be entirely satisfactory. It thus is the principal object of the present invention to provide a rotary valve of the type described in which the shearing of material particles being processed and the jamming of the rotors of such valves by particles trapped between the rotor vanes and the cylindrical wall of the rotor chamber are avoided.